Diagnosis of cystic fibrosis: a high heterogeneity of symptoms and genotypes in a Brazil population.

INTRODUCTION: In highly multiracial populations with inadequate newborn screening, knowledge of the various phenotypic presentations of Cystic Fibrosis (CF) can help reach an early diagnosis. This study aims to describe phenotypes and genotypes at the time of CF diagnosis in a state in the Northeast Region of Brazil. METHODS: Retrospective cross-sectional study. Clinical data were extracted from the medical records of CF patients. Clinical, laboratory, and genotypic characteristics were described for patients admitted to a tertiary referral center between 2007 and 2021. RESULTS: Fifty-eight (58) patients were included in the study, 53.5% of whom were diagnosed through clinical suspicion. The median age at diagnosis was 4.7 months (IQR: 1.5-14.8 months). Five patients had false-negative results in the newborn screening. Faltering growth was the most frequent clinical manifestation. Bronchiectasis and a history of pneumonia predominated in those older than ten, while thinness, underweight, and electrolyte imbalances were more frequent in children under two. Sequencing of the CFTR gene identified 27 genotypes, with at least one class I-III variant in all patients, and nine variants that are rare, previously undescribed, or have uncertain significance (619delA, T12991, K162Q, 3195del6, 1678del > T, 124del123bp, 3121-3113 A > T). The most frequent alleles were p.Phe508del, p.Gly542*, p.Arg334Trp, and p.Ser549Arg. CONCLUSIONS: Malnutrition and electrolyte imbalances were the most frequent phenotypes for children < 2 years and were associated with genotypes including 2 class I-III variants. Rare and previously undescribed variants were identified. The p.Gly542*, p.Arg334Trp, and p.Ser549Arg alleles were among the most frequent variants in this population.

Use of elexacaftor+tezacaftor+ivacaftor in individuals with cystic fibrosis and at least one F508del allele: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the effect of treatment with the combination of three cystic fibrosis transmembrane conductance regulator (CFTR) modulators-elexacaftor+tezacaftor+ivacaftor (ETI)-on important clinical endpoints in individuals with cystic fibrosis. METHODS: This was a systematic review and meta-analysis of randomized clinical trials that compared the use of ETI in individuals with CF and at least one F508del allele with that of placebo or with an active comparator such as other combinations of CFTR modulators, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations and the Patients of interest, Intervention to be studied, Comparison of interventions, and Outcome of interest (PICO) methodology. We searched the following databases: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from their inception to December 26th, 2022. The risk of bias was assessed using the Cochrane risk-of-bias tool, and the quality of evidence was based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE). RESULTS: We retrieved 54 studies in the primary search. Of these, 6 met the inclusion criteria and were analyzed (1,127 patients; 577 and 550 in the intervention and control groups, respectively). The meta-analysis revealed that the use of ETI increased FEV1% [risk difference (RD), +10.47%; 95% CI, 6.88-14.06], reduced the number of acute pulmonary exacerbations (RD, -0.16; 95% CI, -0.28 to -0.04), and improved quality of life (RD, +14.93; 95% CI, 9.98-19.89) and BMI (RD, +1.07 kg/m2; 95% CI, 0.90-1.25). Adverse events did not differ between groups (RD, -0.03; 95% CI, -0.08 to 0.01), and none of the studies reported deaths. CONCLUSIONS: Our findings demonstrate that ETI treatment substantially improves clinically significant, patient-centered outcomes.

A novel high-resolution melting analysis strategy for detecting cystic fibrosis-causing variants.

Cystic fibrosis (CF), an autosomal recessive disease, is caused by variants in both alleles of the CF transmembrane conductance regulator (CFTR) gene. A new assay based on allele-specific polymerase chain reaction and high-resolution melting analysis was developed for the detection of 18 CF-causing CFTR variants previously identified in Cuba and Latin America. The assay is also useful for zygosity determination of mutated alleles and includes internal controls. The reaction mixtures were normalized and evaluated using blood samples collected on filter paper. The evaluation of analytical parameters demonstrated the specificity and sensitivity of the method to detect the included CFTR variants. Internal and external validations yielded a 100% agreement between the new assay and the used reference tests. This assay can complement CF newborn screening not only in Cuba but also in Latin America.

Real-life experience with a generic formulation of lumacaftor-ivacaftor in patients with cystic fibrosis homozygous for the Phe508del CFTR mutation.

INTRODUCTION: Cystic fibrosis (CF) is the most frequent recessive autosomal disorder in the Caucasian population. It is caused by mutations that result in a deficient or dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) protein activity. Among CFTR modulators, potentiator compounds increase channel opening, whereas corrector compounds increase CFTR quantity in the cell surface. OBJECTIVE: To report real-life effects of a generic formulation of lumacaftor-ivacaftor use in patients with CF homozygous for the Phe508del CFTR mutation. PATIENTS AND METHODS: Clinical variables (body mass index [BMI], pulmonary exacerbations, sweat test, and pulmonary function) were analyzed in 30 CF patients homozygous for the Phe508del CFTR mutation, treated with lumacaftor-ivacaftor for 12 months, at the Respiratory Center of Hospital de Niños Ricardo Gutiérrez. These clinical variables were compared with those before the use of modulators. RESULTS: A total of 30 patients with CF homozygous for the Phe508del CFTR mutation receiving lumacaftor-ivacaftor therapy were included in this study. The median (interquartile range [IQR]) age at the start of treatment was 10.79 (7.08-14.05) years. Nineteen patients were male. Before treatment, median (IQR) sweat chloride concentration was 80 (72-92) mEq/L, and it had decreased to 74 (68-78) mEq/L (p = .05) 12 months after treatment. Median (IQR) BMI z-score improved from -0.33 (-0.86 to 0.21) to -0.13 (-0.66 to 0.54) (p = .003). A spirometry was performed in 28 of 30 patients. Median (IQR) ppFEV1 was 83.5 (71-91) before treatment and 86.5 (67-103) after treatment (p = .38), 73.3% of patients referred decreased sputum production and 40% reported improvement in their dyspnea at 12 months. Severe pulmonary exacerbations significantly decreased from 60% in the year before treatment, to 30% at 12 months after treatment (p = .037); 13 patients showed an improvement in their exacerbation rates, 2 showed an increased rate, and 15 showed no change. CONCLUSIONS: The use of a generic formulation of lumacaftor-ivacaftor in patients homozygous for the Phe508del CFTR mutation was associated with improvement in nutritional status and respiratory symptoms, and a significant reduction in severe pulmonary exacerbations.

CFTR modulator therapy: transforming the landscape of clinical care in cystic fibrosis.

Following discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in 1989 and subsequent elucidation of the varied CFTR protein abnormalities that result, a new era of cystic fibrosis management has emerged-one in which scientific principles translated from the bench to the bedside have enabled us to potentially treat the basic defect in the majority of children and adults with cystic fibrosis, with a resultant burgeoning adult cystic fibrosis population. However, the long-term effects of these therapies on the multiple manifestations of cystic fibrosis are still under investigation. Understanding the effects of modulators in populations excluded from clinical trials is also crucial. Furthermore, establishing appropriate disease measures to assess efficacy in the youngest potential trial participants and in those whose post-modulator lung function is in the typical range for people without chronic lung disease is essential for continued drug development. Finally, recognising that a health outcome gap has been created for some people and widened for others who are not eligible for, cannot tolerate, or do not have access to modulators is important.

Brazilian guidelines for the pharmacological treatment of the pulmonary symptoms of cystic fibrosis. Official document of the Sociedade Brasileira de Pneumologia e Tisiologia (SBPT, Brazilian Thoracic Association).

Cystic fibrosis (CF) is a genetic disease that results in dysfunction of the CF transmembrane conductance regulator (CFTR) protein, which is a chloride and bicarbonate channel expressed in the apical portion of epithelial cells of various organs. Dysfunction of that protein results in diverse clinical manifestations, primarily involving the respiratory and gastrointestinal systems, impairing quality of life and reducing life expectancy. Although CF is still an incurable pathology, the therapeutic and prognostic perspectives are now totally different and much more favorable. The purpose of these guidelines is to define evidence-based recommendations regarding the use of pharmacological agents in the treatment of the pulmonary symptoms of CF in Brazil. Questions in the Patients of interest, Intervention to be studied, Comparison of interventions, and Outcome of interest (PICO) format were employed to address aspects related to the use of modulators of this protein (ivacaftor, lumacaftor+ivacaftor, and tezacaftor+ivacaftor), use of dornase alfa, eradication therapy and chronic suppression of Pseudomonas aeruginosa, and eradication of methicillin-resistant Staphylococcus aureus and Burkholderia cepacia complex. To formulate the PICO questions, a group of Brazilian specialists was assembled and a systematic review was carried out on the themes, with meta-analysis when applicable. The results obtained were analyzed in terms of the strength of the evidence compiled, the recommendations being devised by employing the GRADE approach. We believe that these guidelines represent a major advance to be incorporated into the approach to patients with CF, mainly aiming to favor the management of the disease, and could become an auxiliary tool in the definition of public policies related to CF.

Brazilian guidelines for the pharmacological treatment of the pulmonary symptoms of cystic fibrosis. Official document of the Sociedade Brasileira de Pneumologia e Tisiologia (SBPT, Brazilian Thoracic Association)

A fibrose cística (FC) é uma doença genética que resulta em disfunção da proteína reguladora de condutância transmembrana da FC (CFTR), que é um canal de cloro e bicarbonato expresso na porção apical de células epiteliais de diversos órgãos. A disfunção dessa proteína resulta em manifestações clínicas diversas, envolvendo primariamente os sistemas respiratório e gastrointestinal com redução da qualidade e expectativa de vida. A FC ainda é uma patologia incurável, porém o horizonte terapêutico e prognóstico é hoje totalmente distinto e muito mais favorável. O objetivo destas diretrizes foi definir recomendações brasileiras baseadas em evidências em relação ao emprego de agentes farmacológicos no tratamento pulmonar da FC. As perguntas PICO (acrônimo baseado em perguntas referentes aos Pacientes de interesse, Intervenção a ser estudada, Comparação da intervenção e Outcome [desfecho] de interesse) abordaram aspectos relativos ao uso de moduladores de CFTR (ivacaftor, lumacaftor + ivacaftor e tezacaftor + ivacaftor), uso de dornase alfa, terapia de erradicação e supressão crônica de Pseudomonas aeruginosa, e erradicação de Staphylococcus aureus resistente a meticilina e do complexo Burkholderia cepacia. Para a formulação das perguntas, um grupo de especialistas brasileiros foi reunido e realizou-se uma revisão sistemática sobre os temas, com meta-análise quando aplicável. Os resultados encontrados foram analisados quanto à força das evidências compiladas, sendo concebidas recomendações seguindo a metodologia GRADE. Os autores acreditam que o presente documento represente um importante avanço a ser incorporado na abordagem de pacientes com FC, objetivando principalmente favorecer seu manejo, podendo se tornar uma ferramenta auxiliar na definição de políticas públicas relacionadas à FC.

Cystic fibrosis (CF) is a genetic disease that results in dysfunction of the CF transmembrane conductance regulator (CFTR) protein, which is a chloride and bicarbonate channel expressed in the apical portion of epithelial cells of various organs. Dysfunction of that protein results in diverse clinical manifestations, primarily involving the respiratory and gastrointestinal systems, impairing quality of life and reducing life expectancy. Although CF is still an incurable pathology, the therapeutic and prognostic perspectives are now totally different and much more favorable. The purpose of these guidelines is to define evidence-based recommendations regarding the use of pharmacological agents in the treatment of the pulmonary symptoms of CF in Brazil. Questions in the Patients of interest, Intervention to be studied, Comparison of interventions, and Outcome of interest (PICO) format were employed to address aspects related to the use of modulators of this protein (ivacaftor, lumacaftor+ivacaftor, and tezacaftor+ivacaftor), use of dornase alfa, eradication therapy and chronic suppression of Pseudomonas aeruginosa, and eradication of methicillin-resistant Staphylococcus aureus and Burkholderia cepacia complex. To formulate the PICO questions, a group of Brazilian specialists was assembled and a systematic review was carried out on the themes, with meta-analysis when applicable. The results obtained were analyzed in terms of the strength of the evidence compiled, the recommendations being devised by employing the GRADE approach. We believe that these guidelines represent a major advance to be incorporated into the approach to patients with CF, mainly aiming to favor the management of the disease, and could become an auxiliary tool in the definition of public policies related to CF.

Genetic counseling and carrier screening in candidates for gamete donation at a Portuguese center.

OBJECTIVE: Genetic counseling and carrier screening are part of the gamete donation process by healthy individuals. We aim to review the findings of genetic counseling and carrier screening of a cohort of candidates at our public gametes bank. METHODS: Thirty-four male and 64 female candidates had genetic counseling with a medical geneticist before donation. Of these, one female candidate voluntarily dropped-out. Thirty-four males and 63 females performed karyotype and screening for the more common pathogenic variants for CFTR-related cystic fibrosis and spinal muscular atrophy (SMN1) in the Portuguese population. In addition, all females also performed Fragile X expansion screening (FMR1). Thirty candidates with known or assumed African ancestry performed hemoglobinopathies screening. RESULTS: Six candidates were definitely or temporarily withheld from the donation process given their family or personal history that required further investigation. Of 97 candidates tested, 16.5% presented anomalous laboratory results (16/97): ten candidates were carriers for an autosomal recessive disorder - cystic fibrosis (5/97), sickle cell anemia (3/30), and spinal muscular atrophy (2/97). One female was an FMR1 pre-mutation carrier (1/63). One female candidate presented with triple X mosaicism: 47,XXX[2]/46,XX[50]. Two candidates presented with chromosomal instability of unknown origin. In one candidate, a mosaic for the Philadelphia chromosome was detected, revealing the diagnosis of chronic myeloid leukemia. CONCLUSIONS: From a cohort of 97 candidates, 21.7% had a family/personal history or an anomalous laboratory result that required additional genetic counseling, stressing the importance of performing pre-donation genetic counseling in this population.

Five-year performance analysis of a cystic fibrosis newborn screening program in northeastern Brazil.

OBJECTIVE: To analyze the performance of the cystic fibrosis (CF) newborn screening (NBS) program over its first five years in a Brazilian northeastern state. METHOD: A population-based study using a screening algorithm based on immunoreactive trypsinogen (IRT)/IRT. Data were retrieved from the state referral screening center registry. The program performance was evaluated using descriptive indicators such as the results of an active search, coverage, newborn's age at the time of blood sampling, the time between sample collection and its arrival at the laboratory, and the child's age at diagnosis of disease. RESULTS: The public CF screening program covered 82.6% of the 1,017,576 births that occurred, with an accumulated five-year incidence of 1:20,767 live births. The median (25th-75th) age at diagnosis was 3.5 (2.3-7.3) months. The sampling before 7 days of life for the first IRT (IRT1) increased between 2013 and 2017 from 42.2 to 48.3%. Around 5% of IRT1 samples and 30% of the second samples were collected after 30 days of life. In the first and second stages of screening, 23.6% and 19.9% of the infants, respectively, were lost to follow-up. In both stages of screening, the samples were retained at the health units for a median (25th-75th) of 9.0 (7.0-13.0) days. CONCLUSIONS: The coverage by the CF-NBS program was satisfactory as compared to other Brazilian state rates and the percentage of IRT1 samples collected within the first week of life increased progressively. However, time of samples retention at the health units, inappropriate sampling, inherent methodological problems, and loss of follow-up need to improve.

Actualización en fibrosis quística estándares de atención para pacientes con diagnóstico de fibrosis quística con terapia moduladora: informe de la Sociedad Europea de Fibrosis Quística 2023 / Standards of care for patients with a diagnosis of cystic fibrosis who are on modulator therapy: report of the European Fibrosis Cystic Society 2023

La fibrosis quística ha entrado en la era de la terapia específica con los moduladores, útiles en variantes genéticas definidas por estudio molecular, con resultados clínicos exitosos. Este es un resumen de la publicación reciente de la Sociedad Respiratoria Europea que establece los estándares de cuidado para los pacientes que reciben este tratamiento.

Cystic fibrosis has entered the era of specific therapy called modulators, useful in genetic variants defined by molecular study, with successful clinical results. This is a summary of the recent publication of the European Respiratory Society that establishes the standards of care for patients receiving this treatment.

Screening by high-throughput sequencing for pathogenic variants in cystic fibrosis: Benefit of introducing personalized therapies.

This short report documented cystic fibrosis transmembrane conductance regulator (CFTR) variants in 37 patients with cystic fibrosis (CF) in the Rio Grande do Norte region of Northeast Brazil. The high-throughput sequencing technology (HTS) genetic testing provided a definitive molecular diagnosis in 31 patients (83.8%). Among them, 25 patients' carriers of the c.1521_1523delCTT variant, categorized as a class 2 mutation, can be currently treated with CFTR modulator drugs. Five children aged 2-5 years could benefit from double lumacaftor/ivacaftor therapy, and 20 patients aged >6 years could be treated with the triple-combination elexacaftor/tezacaftor/ivacaftor therapy. Thus, the identification of pathogenic variants associated with the development of this disease allows for the introduction of therapy with CFTR modulators that favour better patient management.

Association between phenotypic and genotypic characteristics and disease severity in individuals with cystic fibrosis.

OBJECTIVE: To analyze the association between phenotypic and genotypic characteristics and disease severity in individuals with cystic fibrosis treated at a reference center in Minas Gerais, Brazil. METHODS: This is a retrospective study that collected clinical and laboratory data, respiratory and gastrointestinal manifestations, type of treatment, Shwachman-Kulczycki score, and mutations from the patients' medical records. RESULTS: The sample included 50 participants aged one to 33 years, 50% of whom were female. Out of the one hundred alleles of the Cystic Fibrosis Transmembrane Conductance Regulator gene, the most prevalent mutations were DeltaF508 (45%) and S4X (18%). Mutation groups were only associated with pancreatic insufficiency (p=0.013) and not with disease severity (p=0.073). The latter presented an association with colonization by Pseudomonas aeruginosa and Staphylococcus aureus (p=0.007) and with underweight (p=0.036). Death was associated with age at diagnosis (p=0.016), respiratory symptomatology (p=0.013), colonization (p=0.024), underweight (p=0.017), and hospitalization (p=0.003). CONCLUSIONS: We could identify the association of mutations with pancreatic insufficiency; the association of Staphylococcus aureus colonization and underweight with disease severity; and the lack of association between mutations and disease severity. Environmental factors should be investigated more thoroughly since they seem to have an important effect on disease severity.

Lower airway microbiota and decreasing lung function in young Brazilian cystic fibrosis patients with pulmonary Staphylococcus and Pseudomonas infection.

Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene that leads to respiratory complications and mortality. Studies have shown shifts in the respiratory microbiota during disease progression in individuals with CF. In addition, CF patients experience short cycles of acute intermittent aggravations of symptoms called pulmonary exacerbations, which may be characterized by a decrease in lung function and weight loss. The resident microbiota become imbalanced, promoting biofilm formation, and reducing the effectiveness of therapy. The aim of this study was to monitor patients aged 8-23 years with CF to evaluate their lower respiratory microbiota using 16S rRNA sequencing. The most predominant pathogens observed in microbiota, Staphylococcus (Staph) and Pseudomonas (Pseud) were correlated with clinical variables, and the in vitro capacity of biofilm formation for these pathogens was tested. A group of 34 patients was followed up for 84 days, and 306 sputum samples were collected and sequenced. Clustering of microbiota by predominant pathogen showed that children with more Staph had reduced forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) compared to children with Pseud. Furthermore, the patients' clinical condition was consistent with the results of pulmonary function. More patients with pulmonary exacerbation were observed in the Staph group than in the Pseud group, as confirmed by lower body mass index and pulmonary function. Additionally, prediction of bacterial functional profiles identified genes encoding key enzymes involved in virulence pathways in the Pseud group. Importantly, this study is the first Brazilian study to assess the lower respiratory microbiota in a significant group of young CF patients. In this sense, the data collected for this study on the microbiota of children in Brazil with CF provide a valuable contribution to the knowledge in the field.

High-risk twin pregnancy: case report of an adolescent patient with cystic fibrosis and systemic lupus erythematosus.

BACKGROUND: We present the first case to our knowledge of a spontaneous twin pregnancy in a 16-year-old Caucasian patient with cystic fibrosis and systemic lupus erythematosus. Cystic fibrosis is one of the most common autosomal recessive genetic disorders and primarily affects the respiratory and digestive systems. Systemic lupus erythematosus is a chronic inflammatory disease of unknown cause that affects nearly every organ. Patients with cystic fibrosis or systemic lupus erythematosus are progressively having longer life expectancy and better quality of life, which has led a greater number of female patients reporting the desire to become mothers. CASE PRESENTATION: We present a case of a Caucasian 16-year-old pregnant with twins being treated for both cystic fibrosis and systemic lupus erythematosus. She has two CFTR mutations: p.F508del and 1812_1G>A. In the second trimester, she was admitted for possible preterm labor, which was successfully stopped. The patient's nutritional status worsened, and she had a pulmonary exacerbation as well as a flare of systemic lupus erythematosus. At the 28th gestational week, she presented with a massive hemoptysis episode. The cesarean delivery had no complications, and there were no serious immediate postpartum complications. DISCUSSION AND CONCLUSIONS: While adolescent pregnancies in and of themselves are considered high risk for both the young mothers and their children, they are further complicated when the mother has two chronic diseases and a twin pregnancy. We achieved positive results using a multidisciplinary approach; however, the risks involved were so high that major efforts are to be taken by our medical community to prevent unplanned pregnancies in all patients with cystic fibrosis, especially when a serious comorbidity like the one in this case is present.

Alterations in innate immune responses of patients with chronic rhinosinusitis related to cystic fibrosis.

The role of phagocytes of children with cystic fibrosis (CF) associated with different phenotypes of chronic rhinosinusitis (CRS) is unclear. The aim of this study was to evaluate the phagocytic capacity of blood neutrophils and monocytes and production of superoxide anion by phagocytes in patients with CF with or without chronic rhinosinusitis and with or without nasal polyps (NP). This cross-sectional study was established in 2015-2017 in a tertiary reference center to the CF treatment, Brasilia, Brazil. Sample included 30 children volunteers with CRS related to CF (n = 16) and control subjects (n = 14). Epidemiological and clinical data were compared. Collection of 15 mL of peripheral blood and nasal endoscopy to identify the presence or absence of nasal polyps (NP) were performed. Phagocytosis of Saccharomyces cerevisiae by pathogen-associated molecular pattern receptors and opsonin receptors was assessed. Superoxide anion production was evaluated. The control group showed a higher phagocytic index to monocytes and neutrophils than to the CF or CF+CRS with NP groups [Kruskal-Wallis p = 0.0025] when phagocytosis were evaluated by pathogen-associated molecular pattern receptors (5 yeasts/cell). The phagocytic index of the CF+CRS without NP group was higher than in the CF+CRS with NP group (Kruskal-Wallis p = 0.0168). In the control group, the percentage of phagocytes involved in phagocytosis and superoxide anion production (74.0 ± 9.6%) were higher in all CF groups (p < 0,0001). The innate immune response, represented by phagocytic activity and superoxide anion production by monocytes and neutrophils was more impaired in patients with CF related or not related to CRS than in the control group. However, the phagocytic function of patients without NP showed less impairment.

[Extreme electrolyte depletion associated with septic shock as a form of presentation of cystic fibrosis]. / Depleción electrolítica extrema asociada con shock séptico como forma de presentación de fibrosis quística.

In the pediatric emergency department, dehydrated children are one of the most frequent causes for consultation, however, the coexistence of hyponatremia with hypochloremia and metabolic alkalosis is rare. The presence of metabolic alkalosis due to chloride depletion has been reported as a form of presentation of Cystic Fibrosis (CF). OBJECTIVE: to describe a case of cystic fibrosis of unusual presen tation in a pediatric patient. CLINICAL CASE: we report a 3-month-old previously healthy male infant who presented with internal environment abnormalities consisting of metabolic alkalosis, hypona tremia, hypokalemia, and extreme hypochloremia associated with septic shock due to mixed viral- bacterial pneumonia (Rhino/enterovirus, Streptococcus pneumoniae, and Staphylococcus aureus). Cys tic fibrosis (CF) was suspected, thus the diagnosis was corroborated by sweat test and genetic study which showed the pathogenic variants c.2834C>T (p.Ser945Leu) and c.3484C>T (p.Arg1162X), both heterozygous. CONCLUSION: special attention should be paid to the existence of hypochloremia with metabolic alkalosis and hyponatremia associated or not with pulmonary disease, suspecting CF as the first option. This consideration becomes more relevant in those countries where the neonatal screening test is not widely available.

Net benefit of ivacaftor during prolonged tezacaftor/elexacaftor exposure in vitro.

BACKGROUND: A decrease in the lumacaftor-mediated increase in F508del-CFTR function and expression upon prolonged exposure to ivacaftor (VX-770) has previously been described. However, the efficacy observed with ivacaftor-containing CFTR modulator therapies in vivo is in conflict with these reports. We hypothesized that a portion of the apparent decrease in CFTR function observed after prolonged ivacaftor exposure in vitro was due to an increase in constitutive CFTR-mediated ion transport. METHODS: Human nasal epithelial (HNE) cells were obtained by brushings from three CF individuals homozygous for the F508del CFTR mutation. Differentiated epithelia were pre-treated with prolonged (24 h) exposure to either lumacaftor (VX-809; 3 µM), tezacaftor (VX-661; 3 µM), elexacaftor (VX-445; 3 µM), and/or ivacaftor (0.1-6.4 µM) or DMSO (vehicle control), and CFTR function was assayed by Ussing chamber electrophysiology. RESULTS: In cells treated with lumacaftor, constitutive CFTR activity was not increased at any concentration of co-treatment with ivacaftor. Constitutive CFTR activity was also unchanged in cells treated with the combination of tezacaftor and elexacaftor. An increase in constitutive CFTR activity above the DMSO controls was only observed in cells treated with the combination of tezacaftor and elexacaftor and co-treated with at least 0.1 µM ivacaftor. CONCLUSIONS: These results demonstrate that ivacaftor is a critical component in the triple combination therapy along with tezacaftor and elexacaftor to increase constitutive CFTR function. This work further elucidates the mechanism of action of the effective triple combination therapeutic that is now the primary clinical tool in treating CF.

Pancreatic Insufficiency in a Child with p.Gly542* and c.2657+5G>A Heterozygote CFTR: A Case Report.

Cystic fibrosis is a monogenic and autosomal recessive disease. It is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator gene responsible for encoding the CFTR protein. Involvement of the gastrointestinal and respiratory systems is the main clinical manifestation. In this case, we report a heterozygous CFTR patient harboring class I (p.Gly542*) and class V (c.2657+5G>A) mutations. The importance of this case report lies in the clinical features because the patient, aged 3 years, presented with early exocrine pancreatic insufficiency, which can be considered atypical, as most individuals with this genotype are pancreatic sufficient or develop pancreatic insufficiency later in life. This report aims at presenting the tests requested that contributed to the patient's diagnosis, as well as at understanding the association between these mutations and their phenotypic presentation. Interpretation of the genotype-phenotype relationship represents a challenge, as genetic analysis alone is not sufficient to clearly predict severity of the disease. This is because the significant phenotypic heterogeneity existing among patients with the same genotype may exert socioeconomic and sociocultural influences, or by the action of CFTR modifiers, such as environmental and modifying genes, which can alter the protein's function and exert an impact on the individual's phenotype.